/*
 * FreeRTOS Kernel V10.5.1
 * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
 *
 * SPDX-License-Identifier: MIT
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * https://www.FreeRTOS.org
 * https://github.com/FreeRTOS
 *
 */

/*
 * A sample implementation of pvPortMalloc() and vPortFree() that permits
 * allocated blocks to be freed, but does not combine adjacent free blocks
 * into a single larger block (and so will fragment memory).  See heap_4.c for
 * an equivalent that does combine adjacent blocks into single larger blocks.
 *
 * See heap_1.c, heap_3.c and heap_4.c for alternative implementations, and the
 * memory management pages of https://www.FreeRTOS.org for more information.
 */
#include <stdlib.h>
#include <string.h>

/* Defining MPU_WRAPPERS_INCLUDED_FROM_API_FILE prevents task.h from redefining
 * all the API functions to use the MPU wrappers.  That should only be done when
 * task.h is included from an application file. */
#define MPU_WRAPPERS_INCLUDED_FROM_API_FILE

#include "FreeRTOS.h"
#include "task.h"

#undef MPU_WRAPPERS_INCLUDED_FROM_API_FILE

#if (configSUPPORT_DYNAMIC_ALLOCATION == 0)
    #error This file must not be used if configSUPPORT_DYNAMIC_ALLOCATION is 0
#endif

#ifndef configHEAP_CLEAR_MEMORY_ON_FREE
    #define configHEAP_CLEAR_MEMORY_ON_FREE 0
#endif

/* A few bytes might be lost to byte aligning the heap start address. */
#define configADJUSTED_HEAP_SIZE (configTOTAL_HEAP_SIZE - portBYTE_ALIGNMENT)

/* Assumes 8bit bytes! */
#define heapBITS_PER_BYTE ((size_t)8)

/* Max value that fits in a size_t type. */
#define heapSIZE_MAX (~((size_t)0))

/* Check if multiplying a and b will result in overflow. */
#define heapMULTIPLY_WILL_OVERFLOW(a, b) (((a) > 0) && ((b) > (heapSIZE_MAX / (a))))

/* Check if adding a and b will result in overflow. */
#define heapADD_WILL_OVERFLOW(a, b) ((a) > (heapSIZE_MAX - (b)))

/* MSB of the xBlockSize member of an BlockLink_t structure is used to track
 * the allocation status of a block.  When MSB of the xBlockSize member of
 * an BlockLink_t structure is set then the block belongs to the application.
 * When the bit is free the block is still part of the free heap space. */
#define heapBLOCK_ALLOCATED_BITMASK         (((size_t)1) << ((sizeof(size_t) * heapBITS_PER_BYTE) - 1))
#define heapBLOCK_SIZE_IS_VALID(xBlockSize) (((xBlockSize)&heapBLOCK_ALLOCATED_BITMASK) == 0)
#define heapBLOCK_IS_ALLOCATED(pxBlock)     (((pxBlock->xBlockSize) & heapBLOCK_ALLOCATED_BITMASK) != 0)
#define heapALLOCATE_BLOCK(pxBlock)         ((pxBlock->xBlockSize) |= heapBLOCK_ALLOCATED_BITMASK)
#define heapFREE_BLOCK(pxBlock)             ((pxBlock->xBlockSize) &= ~heapBLOCK_ALLOCATED_BITMASK)

/*-----------------------------------------------------------*/

/* Allocate the memory for the heap. */
#if (configAPPLICATION_ALLOCATED_HEAP == 1)

/* The application writer has already defined the array used for the RTOS
 * heap - probably so it can be placed in a special segment or address. */
extern uint8_t ucHeap[configTOTAL_HEAP_SIZE];
#else
PRIVILEGED_DATA static uint8_t ucHeap[configTOTAL_HEAP_SIZE];
#endif /* configAPPLICATION_ALLOCATED_HEAP */

/* Define the linked list structure.  This is used to link free blocks in order
 * of their size. */
typedef struct A_BLOCK_LINK {
    struct A_BLOCK_LINK *pxNextFreeBlock; /*<< The next free block in the list. */
    size_t xBlockSize; /*<< The size of the free block. */
} BlockLink_t;

static const uint16_t heapSTRUCT_SIZE = ((sizeof(BlockLink_t) + (portBYTE_ALIGNMENT - 1)) & ~((size_t)portBYTE_ALIGNMENT_MASK));
#define heapMINIMUM_BLOCK_SIZE ((size_t)(heapSTRUCT_SIZE * 2))

/* Create a couple of list links to mark the start and end of the list. */
PRIVILEGED_DATA static BlockLink_t xStart, xEnd;

/* Keeps track of the number of free bytes remaining, but says nothing about
 * fragmentation. */
PRIVILEGED_DATA static size_t xFreeBytesRemaining = configADJUSTED_HEAP_SIZE;

/*-----------------------------------------------------------*/

/*
 * Initialises the heap structures before their first use.
 */
static void prvHeapInit(void) PRIVILEGED_FUNCTION;

/*-----------------------------------------------------------*/

/* STATIC FUNCTIONS ARE DEFINED AS MACROS TO MINIMIZE THE FUNCTION CALL DEPTH. */

/*
 * Insert a block into the list of free blocks - which is ordered by size of
 * the block.  Small blocks at the start of the list and large blocks at the end
 * of the list.
 */
#define prvInsertBlockIntoFreeList(pxBlockToInsert)                                                                                  \
    {                                                                                                                                \
        BlockLink_t *pxIterator;                                                                                                     \
        size_t xBlockSize;                                                                                                           \
                                                                                                                                     \
        xBlockSize = pxBlockToInsert->xBlockSize;                                                                                    \
                                                                                                                                     \
        /* Iterate through the list until a block is found that has a larger size */                                                 \
        /* than the block we are inserting. */                                                                                       \
        for (pxIterator = &xStart; pxIterator->pxNextFreeBlock->xBlockSize < xBlockSize; pxIterator = pxIterator->pxNextFreeBlock) { \
            /* There is nothing to do here - just iterate to the correct position. */                                                \
        }                                                                                                                            \
                                                                                                                                     \
        /* Update the list to include the block being inserted in the correct */                                                     \
        /* position. */                                                                                                              \
        pxBlockToInsert->pxNextFreeBlock = pxIterator->pxNextFreeBlock;                                                              \
        pxIterator->pxNextFreeBlock = pxBlockToInsert;                                                                               \
    }
/*-----------------------------------------------------------*/

void *pvPortMalloc(size_t xWantedSize) {
    BlockLink_t *pxBlock;
    BlockLink_t *pxPreviousBlock;
    BlockLink_t *pxNewBlockLink;
    PRIVILEGED_DATA static BaseType_t xHeapHasBeenInitialised = pdFALSE;
    void *pvReturn = NULL;
    size_t xAdditionalRequiredSize;

    vTaskSuspendAll();
    {
        /* If this is the first call to malloc then the heap will require
         * initialisation to setup the list of free blocks. */
        if (xHeapHasBeenInitialised == pdFALSE) {
            prvHeapInit();
            xHeapHasBeenInitialised = pdTRUE;
        }

        if (xWantedSize > 0) {
            /* The wanted size must be increased so it can contain a BlockLink_t
             * structure in addition to the requested amount of bytes. Some
             * additional increment may also be needed for alignment. */
            xAdditionalRequiredSize = heapSTRUCT_SIZE + portBYTE_ALIGNMENT - (xWantedSize & portBYTE_ALIGNMENT_MASK);

            if (heapADD_WILL_OVERFLOW(xWantedSize, xAdditionalRequiredSize) == 0) {
                xWantedSize += xAdditionalRequiredSize;
            } else {
                xWantedSize = 0;
            }
        }

        /* Check the block size we are trying to allocate is not so large that the
         * top bit is set.  The top bit of the block size member of the BlockLink_t
         * structure is used to determine who owns the block - the application or
         * the kernel, so it must be free. */
        if (heapBLOCK_SIZE_IS_VALID(xWantedSize) != 0) {
            if ((xWantedSize > 0) && (xWantedSize <= xFreeBytesRemaining)) {
                /* Blocks are stored in byte order - traverse the list from the start
                 * (smallest) block until one of adequate size is found. */
                pxPreviousBlock = &xStart;
                pxBlock = xStart.pxNextFreeBlock;

                while ((pxBlock->xBlockSize < xWantedSize) && (pxBlock->pxNextFreeBlock != NULL)) {
                    pxPreviousBlock = pxBlock;
                    pxBlock = pxBlock->pxNextFreeBlock;
                }

                /* If we found the end marker then a block of adequate size was not found. */
                if (pxBlock != &xEnd) {
                    /* Return the memory space - jumping over the BlockLink_t structure
                     * at its start. */
                    pvReturn = (void *)(((uint8_t *)pxPreviousBlock->pxNextFreeBlock) + heapSTRUCT_SIZE);

                    /* This block is being returned for use so must be taken out of the
                     * list of free blocks. */
                    pxPreviousBlock->pxNextFreeBlock = pxBlock->pxNextFreeBlock;

                    /* If the block is larger than required it can be split into two. */
                    if ((pxBlock->xBlockSize - xWantedSize) > heapMINIMUM_BLOCK_SIZE) {
                        /* This block is to be split into two.  Create a new block
                         * following the number of bytes requested. The void cast is
                         * used to prevent byte alignment warnings from the compiler. */
                        pxNewBlockLink = (void *)(((uint8_t *)pxBlock) + xWantedSize);

                        /* Calculate the sizes of two blocks split from the single
                         * block. */
                        pxNewBlockLink->xBlockSize = pxBlock->xBlockSize - xWantedSize;
                        pxBlock->xBlockSize = xWantedSize;

                        /* Insert the new block into the list of free blocks. */
                        prvInsertBlockIntoFreeList((pxNewBlockLink));
                    }

                    xFreeBytesRemaining -= pxBlock->xBlockSize;

                    /* The block is being returned - it is allocated and owned
                     * by the application and has no "next" block. */
                    heapALLOCATE_BLOCK(pxBlock);
                    pxBlock->pxNextFreeBlock = NULL;
                }
            }
        }

        traceMALLOC(pvReturn, xWantedSize);
    }
    (void)xTaskResumeAll();

#if (configUSE_MALLOC_FAILED_HOOK == 1)
    {
        if (pvReturn == NULL) {
            vApplicationMallocFailedHook();
        }
    }
#endif

    return pvReturn;
}
/*-----------------------------------------------------------*/

void vPortFree(void *pv) {
    uint8_t *puc = (uint8_t *)pv;
    BlockLink_t *pxLink;

    if (pv != NULL) {
        /* The memory being freed will have an BlockLink_t structure immediately
         * before it. */
        puc -= heapSTRUCT_SIZE;

        /* This unexpected casting is to keep some compilers from issuing
         * byte alignment warnings. */
        pxLink = (void *)puc;

        configASSERT(heapBLOCK_IS_ALLOCATED(pxLink) != 0);
        configASSERT(pxLink->pxNextFreeBlock == NULL);

        if (heapBLOCK_IS_ALLOCATED(pxLink) != 0) {
            if (pxLink->pxNextFreeBlock == NULL) {
                /* The block is being returned to the heap - it is no longer
                 * allocated. */
                heapFREE_BLOCK(pxLink);
#if (configHEAP_CLEAR_MEMORY_ON_FREE == 1)
                {
                    (void)memset(puc + heapSTRUCT_SIZE, 0, pxLink->xBlockSize - heapSTRUCT_SIZE);
                }
#endif

                vTaskSuspendAll();
                {
                    /* Add this block to the list of free blocks. */
                    prvInsertBlockIntoFreeList(((BlockLink_t *)pxLink));
                    xFreeBytesRemaining += pxLink->xBlockSize;
                    traceFREE(pv, pxLink->xBlockSize);
                }
                (void)xTaskResumeAll();
            }
        }
    }
}
/*-----------------------------------------------------------*/

size_t xPortGetFreeHeapSize(void) {
    return xFreeBytesRemaining;
}
/*-----------------------------------------------------------*/

void vPortInitialiseBlocks(void) {
    /* This just exists to keep the linker quiet. */
}
/*-----------------------------------------------------------*/

void *pvPortCalloc(size_t xNum,
    size_t xSize) {
    void *pv = NULL;

    if (heapMULTIPLY_WILL_OVERFLOW(xNum, xSize) == 0) {
        pv = pvPortMalloc(xNum * xSize);

        if (pv != NULL) {
            (void)memset(pv, 0, xNum * xSize);
        }
    }

    return pv;
}
/*-----------------------------------------------------------*/

static void prvHeapInit(void) /* PRIVILEGED_FUNCTION */
{
    BlockLink_t *pxFirstFreeBlock;
    uint8_t *pucAlignedHeap;

    /* Ensure the heap starts on a correctly aligned boundary. */
    pucAlignedHeap = (uint8_t *)(((portPOINTER_SIZE_TYPE)&ucHeap[portBYTE_ALIGNMENT - 1]) & (~((portPOINTER_SIZE_TYPE)portBYTE_ALIGNMENT_MASK)));

    /* xStart is used to hold a pointer to the first item in the list of free
     * blocks.  The void cast is used to prevent compiler warnings. */
    xStart.pxNextFreeBlock = (void *)pucAlignedHeap;
    xStart.xBlockSize = (size_t)0;

    /* xEnd is used to mark the end of the list of free blocks. */
    xEnd.xBlockSize = configADJUSTED_HEAP_SIZE;
    xEnd.pxNextFreeBlock = NULL;

    /* To start with there is a single free block that is sized to take up the
     * entire heap space. */
    pxFirstFreeBlock = (BlockLink_t *)pucAlignedHeap;
    pxFirstFreeBlock->xBlockSize = configADJUSTED_HEAP_SIZE;
    pxFirstFreeBlock->pxNextFreeBlock = &xEnd;
}
/*-----------------------------------------------------------*/
